It is worth mentioning that the expressions “artificial covering units”, “stone” and “flagstone” are used throughout the present description without distinction to define a flat slab of stone used as a paving or building material. Artificial covering units or artificial stones, which are generally made of concrete, are well-known to lay out pavements or covering wall surfaces on residential or commercial properties, for example for defining the surface of walkways or patios. Such artificial covering units are advantageously relatively inexpensive to manufacture, as opposed to natural carved flagstones, but the resulting pattern is often repetitive or has what is called in this field an unnatural “linear line effect”. Great efforts are therefore being made to design artificial stones which provide a more natural look, creating the effect of old world craftsmanship, while still retaining the ease of their manufacture.
One example of a prior art artificial flagstone is the flagstone marketed under the trademark Kusel-Form. One drawback however with that prior art flagstone, which is provided with regular segments, is that it still does not provide a satisfactory old natural look. It still looks artificial.
Other attempts have been made in the past to develop sets of artificial stones comprising stones of different shapes used in combination with each other for paving a surface. The natural random look in those cases is obtained by combining artificial stones of different shapes. A major drawback however with those sets is that it often becomes a real puzzle for a user to install and combine those stones in a proper way.
Known to the Applicant are U.S. Pat. No. 6,881,463 and US2006/0182923, and US applications 2007/0077387 and 2007/0098945, all from RICCOBENE.
U.S. Pat. No. 6,881,463 concerns a surface covering unit comprising primary units which are rotational tessellation of one another. US2006/0182923 concerns a building unit having three vertices and a pair of sides extending from each vertex, the sides of a pair being rotational images of each other. US application 2007/0077387 discloses a building unit resembling the one from US2006/0182923 for which two of its sides may have a midpoint bisecting the sides in two portions, each portion being a rotational image of the other portion. US application 2007/0098945 is a republication of US application 2006/0182923. This republished application discloses sides of the building unit which all comprise a series of straight-line segments, the segment being angled relative to at least one adjacent segment such that the general appearance of the sides is irregular.
Also known to the Application is Japanese patent P2004-124634 (IDO). This patent concerns a block having pairs of neighbouring sides, the first side of a pair having a shape which is a “negative” image of the shape of the other side of the pair. The sides of such pair are also provided with indicators (or index) that facilitate the matching of adjacent blocks during their installation.
In Canadian patent No. 2,569,998, the Applicant of the present invention improved over the prior art artificial stones in providing an asymmetrical artificial flagstone having six irregular sides. Indeed, the split deviations provided on the sides provide an irregular profile that gives the flagstone a more natural look. This artificial flagstone is particularly advantageous since it makes it possible to obtain a pavement with an improved natural random look by simply using a plurality of artificial flagstones having all the same shape. In order to guide the user during the laying out of the stones on a surface, the stones may be provided with distinctive markers thereon.
Even if the above-described flagstones proposed by the Applicant of the present invention are satisfactory, there is still a need for an improved artificial covering unit that would provide a surface with an even improved natural random look, while, at the same time, being easy to manufacture at a reasonable cost and easy to install for any unskilled person.